In general, I don't think it's the case that whole DF parties are evil, but rather that you get That One Guy who is evil. The one who starts whining and complaining and tossing insults around whenever things don't go perfectly on the first try. The one who THINKS he's saying what everyone else is secretly thinking and is the only one with the cajones to say it out loud, when really no one agrees with him at all and his foul attitude is causing morale to plummet.

Don't be That One Guy. It never helps.